Valve

ABSTRACT

The invention relates to a valve comprising a valve housing (2) which, for transport of a heatable fluid such as hydraulic oil, has at least one utility connection (A, B), at least one pressure supply connection (P), and at least one return connection (T1, T2), and a control slide (6) which is guided in the valve housing (2) in a longitudinally displaceable manner. The valve is characterised in that, in at least one position of the control slide (6), in which position the pressure supply connection (P) is at least partially separated from the utility connection (A, B), the heatable fluid arrives, proceeding from this pressure supply connection (P) and via a heat-emitting connection in the control slide (6), at the at least one return connection (T1, T2) as a loss volume flow which, serving as a heat source, heats at least regions of the control slide (6).

The invention relates to a valve having a valve housing which, fortransporting a heatable fluid such as hydraulic fluid, has at least oneutility port, at least one pressure supply port, and at least one returnport and a valve spool that is guided in a longitudinally displaceablemanner in the valve housing.

WO 2008/098559 A1 discloses a control block having a plurality ofcontrol block elements, in each of which elements a valve assembly foractuating a corresponding hydraulic consumer is provided, wherein thecontrol block has an oil channel, through which an oil flow forcontrolling the temperature of at least one control block element flowsindependently of the actuation of the valve assembly. Even when a valvespool of the control block is not actuated for a prolonged period, it isthus possible to ensure that it is heated such that a jamming of theassociated valve spool is prevented upon actuation of a valve.

In the prior art solution, provision is preferably made such that theoil flow is essentially constant, as in this manner a uniform heating ofthe valve housing can be ensured. However, maintaining a constant oilflow requires continuous pump output, which in turn requires energy, andbecause the valve spool is heated indirectly via the valve housinghaving the oil channel, the energy transfer from the valve housing tothe valve spool inevitably leads to energy losses, which likewiseincreases the energy input required to heat the valve spool. It alsotakes time until the valve spool, starting from the valve housing, isheated. A jamming of the valve spool in the valve therefore cannot bereliably prevented, especially under cold starting conditions.

Starting from this prior art, the invention is based on the object ofproviding a solution that is an improvement over the prior art. Thisobject is achieved by a valve having the features of Claim 1 in itsentirety.

Because of the fact that according to the characterizing part of Claim1, in at least one position of the valve spool in which the pressuresupply port is at least partially disconnected from the utility port,the heatable fluid arrives, starting from this pressure supply port andvia a heat-emitting connection in the valve spool, at the at least onereturn port as slippage which, serving as a heat source, heats at leastareas of the valve spool, it is ensured that the relevant areas of thevalve spool are heated directly and quickly so as to ensure that evenunder very cold conditions, the valve spool cannot jam in the valvehousing during operation of the valve.

Because the slippage, which is preferably heated via a barrier devicethat serves as a fluid resistance, transfers heat directly due tofriction to the ingoing and/or outgoing fluid in the valve spool, only asmall flow rate is needed for “heating” the valve spool. This flow ratecan be provided to the valve with low pump output and is otherwisestopped as soon as the valve ensures a pressure supply, starting fromits pressure supply source, at its hydraulic utility port to which ahydraulic consumer such as a power cylinder can be hooked up. Becauserelatively high flow rates compared to the aforementioned slippage aregenerally needed for the actuation of such a hydraulic consumer in anycase, the hydraulic valve, because it is operating under a load, willhave already reached its desired operating temperature, whichcounteracts a jamming of the valve spool and thus makes it unnecessaryto provide a permanent volumetric flow as a heating medium forcontinuous heating, as is the case in the prior art.

In a preferred embodiment of the valve according to the invention,provision is made such that the slippage can be heated via a barrierdevice which, serving as a fluid resistance, transfers heat generated byfriction to the fluid entering and/or exiting the valve spool. Theresulting frictional heat can thus be transferred to the fluid as a heatcarrier in a particularly energy efficient manner.

In another preferred embodiment of the valve according to the invention,the barrier device has at least one type of control diaphragm, of whichthe free diaphragm cross section in the control mode results from aclosing motion of the valve spool with respect to the valve housing inthe area of the one pressure supply port and/or of the one return port,into which port or into which ports the heat emitting connection in thevalve spool opens. Because the barrier device is integrated in the valvehousing and is actuated by the movable valve spool in such a manner, theheat-generating and heat-emitting device is thus received in the valvein a particularly space-saving manner.

In another preferred embodiment of the valve according to the invention,provision is made such that, with increasing widening of the diaphragmcross section of the one type of control diaphragm at the one pressuresupply port with simultaneous narrowing of the same at the one returnport, by means of a further type of control diaphragm, of which the freediaphragm cross section in the control mode results from a closingmotion of the valve spool with respect to the valve housing in the areaof the one assignable utility port, the flow rate from this one pressuresupply port to this one assignable utility port increases. By means ofeach other type of control diaphragm, a fluid flow to or from thecorresponding utility port can be used as a type of further, additionalbarrier device in order to increase the input of heat into the fluid bythe frictional heat generated by throttling said fluid.

In the valve according to the invention, the heat-emitting connection inthe valve spool is preferably formed by a longitudinal channel, which inthe control mode exits at least partially toward the one pressure supplyport and the one return port by means of cross channels. Thelongitudinal and cross channel routing inside the valve spool leads torapid heating of the latter such that heat input occurs directly on thevalve spool, which considerably reduces the tendency of the latter tostick and jam in the valve housing under cold operating conditions. Theclosing and opening of the one type of control diaphragm fluidicallysupports the respective closing and opening of the further type ofcontrol diaphragm and vice versa.

Other advantageous embodiments of the valve according to the inventionare the subject matter of the further sub-claims.

An individual pressure compensator, which provides a control pressure atthe pressure supply port P of the valve and thus advantageously rendersthe slippage independent of the pump pressure, can be arrangedhydraulically upstream of the valve.

The invention is explained in more detail in the following, withreference to an exemplary embodiment illustrated in the figures.

Shown are:

FIG. 1 the valve according to the invention, partially in whole view,partially in a sectional view; and

FIG. 2 an illustration corresponding to FIG. 1, but with the valve spooldepicted in a longitudinal sectional view.

The valve according to the invention shown in the figures has a valvehousing 2, in which a valve spool 6 is displaceably guided in alongitudinal guide 4. Viewed toward the figures, the valve housing 2 iscut off at its lower end and thus only illustrated in part for easierviewing. Fluid connection points such as the two utility ports A, B, towhich a hydraulic consumer in the form of, say, a power cylinder orhydraulic motor and not shown in any further detail can be connected,are formed in the valve housing 2. A centrally arranged pressure supplyport P and two tank or return ports T1, T2 arranged adjacently theretoon the right and the left engage with the valve housing 2, on the sideopposite the utility ports A, B.

At their respective ends facing away from the consumer, the two utilityports A, B open into a control chamber 8 or 10, respectively. At itsupper end, the pressure supply port P opens into a further controlchamber 12. Said control chambers 8, 10, 12 encompass, on the outercircumference thereof, the valve spool 6 inside the valve housing 2 andabut on the longitudinal guide 4. In the middle or neutral position ofthe valve spool shown in FIG. 6, in which the fluid passage of thepressure supply port P is separated from the corresponding utility portA, B, areas 14, 16 of the valve spool 6, which are reduced in diameter,are arranged completely inside the two control chambers 8 and 10,respectively. Each corresponding control chamber 8, 10, 12, viewed inthe longitudinal alignment of the valve spool 6 inside the valve housing2, in turn has two opposing cylindrical wall sections 18, which areessentially configured identically for all control chambers. Cylindricalwall sections 20, which are comparable in configuration to the wallsections 18, delimit two fluid chambers 22, 24, which according to theillustration in the figures do not encompass the valve spool 6 all ofthe way to the bottom, wherein the lower annular sections 26 of theassociated wall sections 20 open into the return ports T1, T2 and atleast partially delimit the latter at the edge. In addition, twopressure relief valves 28, which act as safety valves to preventpressure overloading, open into the two fluid chambers 22, 24. Whereasthe pressure supply port P opens into the valve housing 2 in alongitudinal direction within the drawing plane, the two return portsT1, T2 open into the valve housing 2 in a direction that isperpendicular to the drawing plane.

Individual control grooves 30, which are at least partiallywedge-shaped, are formed on both sides of each recessed area 14, 16 ofthe valve spool 6, on the circumference thereof. The free ends of thecontrol grooves 30, facing one another, open into the associated controlchambers 8 and 10, respectively, at least in the illustrated middle orneutral position of the valve spool 6. Depending upon the travelposition of the valve spool 6, the other free end of a control groove 30then moves, in a media-conducting manner, into the wall sections 18 ofthe further control chamber 12 or into the associated wall sections 20of the two fluid chambers 22 or 24, respectively. The individual controlgrooves 30 of the valve spool 6, together with wall parts of the valvehousing, which delimit the aforesaid wall sections 20 of the fluidchambers 22, 24 and the wall sections 18 of the control chamber 12, thusform control diaphragms, which shall henceforth be designated as furthercontrol diaphragms in order to distinguish them from additional controldiaphragms, which shall be explained in more detail.

Viewed toward the figures, on its left end the valve housing 2 isprovided with an end part 32, which has a compression spring assembly 34for returning the valve spool 6 to its illustrated neutral or middleposition, wherein the illustrated compression spring extends between twocap parts 36, 38, of which one cap part 36 is arranged stationarily inthe end part 32 and the further cap part 38 can be moved toward thefirst cap part 36 against the action of the compression spring. For thetravel movement of the second cap part 38, the latter is in abutmentwith the free left end face of the valve spool 6 via a flange. The cappart 38 can furthermore be guided in a longitudinally displaceablemanner in the cap part 36 using a pin guide 40 via an opening in the cappart 36, wherein the free end of the displacement pin in conjunctionwith the inside wall of the cap-like end part 32 constitutes a stop or atravel limiter for the left side of the valve spool 6.

Arranged on the right-hand side of the end face of the valve housing 2is a further, second end part 42, which is equipped with two independentpilot valves 44 for actuating the valve. A section of the valve spool 6itself that is narrower in diameter engages with the second end part 42,wherein the second end part 42 is equipped with a manually adjustablestop device 46 such that the maximum stroke of the valve spool 6 can belimited accordingly. Furthermore, a swiveling crank drive 48 engageswith the free end area of the valve spool 6, on the right-hand sidethereof, in order to enable an emergency actuation by hand should theneed arise. The end parts 40, 42 are components of the valve housing 2of the valve according to the invention.

The valve assembly described in the preceding is disclosed in thepost-published document DE 10 2016 011 860.1 of the Patent Holder suchthat the design itself shall not be discussed in any further detailhere. In this context, it should merely be mentioned that the pressuresupply port P can be supplied directly with the fluid pressure of ahydraulic pump. However, according to the aforementioned post-publishedpatent document, the pressure supply port P could also be connected tothe pressure-supplying port of a so-called individual pressurecompensator, as shown by way of example in FIG. 1 of this propertyright.

As FIG. 2 in particular shows, the essentially cylindrical valve spool 6is traversed, at least in part, along its center or longitudinal axis bya longitudinal channel 50 in the nature of a drilled hole. Viewed towardFIG. 2, the left end of the longitudinal channel 50 opens into the freeend face of the valve spool 6 and is closed in this area in amedia-tight manner by a sealing plug assembly 52. On its right side, thelongitudinal channel 50 opens into a blind hole inside the valve slide6. There are three cross channels 54, 56 and 58 arranged transversely toand opening into this longitudinal channel 50 for the passage of fluid.At their free ends, these cross channels 54, 56, 58 open on oppositesides at the surface of the valve spool 6. The lower free end, via whichthe corresponding cross channel 54, 56, 58 exits at the top of the valvespool, is denoted by 59 in FIG. 1. For a better display, the valve spool6 in FIG. 1 is depicted as turned slightly toward the observer comparedto the illustration in FIG. 2. Viewed toward the figures, in the middleor neutral position of the valve spool 6 the left cross channel 54opens, with an approximately 50 percent overlap in each case, into theright wall section 20 of the fluid chamber 22 and into the wall partsadjacent thereto on the right of the valve housing 2. Viewed toward FIG.2, the two opposite free ends of the further, middle cross channel 56open at an overlap of approximately 50 percent each into the left wallsection 18 of the control chamber 12 and into the wall parts adjacentthereto of the valve housing 2. 50 percent of the two opposite free endsof the rightmost cross channel 58 in the viewing direction also openinto the right wall section 20 of the right fluid chamber 24 and intothe wall parts of the valve housing 2 adjacent thereto of the valvehousing 2, which delimit the wall section 20 to the right. The wallsections 18 thus form cylindrical chambers, which merge seamlessly intothe control chambers 8, 10 and encompass the valve spool 6 with the sameradial spacing.

In the lower area of the valve housing 2, the cross channels 54 and 58thus open into the right left annular section 26 as part of theassociated wall sections 20 of the fluid chambers 22 and 24, in the areaof the return ports T1 and T2. The wall sections 20 with the associatedannular sections 26 furthermore surround the valve spool 6 at apredefinable constant radial spacing, except for where the return portsT1, T2 engage with the valve housing 2. One type of control diaphragm60, 62 and 64 is formed at the point where the corresponding crosschannel 54, 56, 58 transitions into the adjacent wall parts of the valvehousing 2, wherein depending upon the travel direction of the valvespool 6, the respective control diaphragms 60, 62, 64 widen or narrow,respectively, with regard to their free diameters. The respectivecontrol diaphragms 60, 62, 64 thus form a type of barrier device, whichimpedes the flow of the fluid such as hydraulic fluid, which isinitially cold at the start of operation, from the pressure supply portP via the cross channel 62 into the longitudinal channel 50 and fromthere back to the return ports T1 and T2 via the corresponding crosschannels 54 and 58 serving as outlets.

Even if the valve is not in operation, as depicted in FIGS. 1 and 2, andthe valve spool 6 has assumed its middle or neutral position showntherein, the barrier device can still be used to heat first the interiorof the valve spool 6 and then the whole valve spool 6 using a relativelylow slippage at the pressure supply port P with the frictional heatarising at the illustrated control diaphragms 60, 62, 64, which thusprevents the valve spool 6 from sticking and jamming in the longitudinalguide 4 during operation of the valve under cold conditions. In thefrictional heat-generating position of the valve spool 6, the latter isin its left (viewed toward the figures) stop position with its free endin abutment on the cap part 38.

Viewed toward the figures and if the valve spool 6 is slid to the left,for example, the control grooves 30 arranged on the left side in thearea of the utility port B come into fluidic connection with the controlchamber 12 with the pressure supply port P conducting fluid at apredefinable pressure, to the effect that the utility port B, with itsconnected hydraulic consumer, is then supplied with fluid via itscontrol chamber 10. Any return-flowing fluid originating from thehydraulic consumer is then discharged, via the utility port A and theleft control chamber 8 and by means of the control grooves 30 arrangedon the left side in the valve spool 6, into the left fluid chamber 22,from where it is then supplied to the return port T1. In the relevantvalve position, the further return port T2 is then closed off from theadjacently arranged utility port B. With the relevant travel movement ofthe valve slide 6, the control diaphragms 60, 64 at the return ports T1and T2, respectively, are widened with respect to their free diametersand the free cross section of the control diaphragm 62 at the pressuresupply port P is narrowed such that the frictional heat decreases at thediaphragms 60, 64 and increases at the diaphragm 62 until the latter iscompletely closed off from the adjacent housing parts of the valvehousing. Preferably preheated fluid thus flows in the return circuitfrom the utility port A via the fluid chamber 22 to the return port T1,specifically via the cross channel 54, which is narrowed with respect tothe longitudinal channel 50 to the effect that the fluid, even in thereturn circuit, can still be heated further by frictional heat.

As explained, during this process the return port 2 remains closed suchthat no heating within the fluid occurs in this area. With a rightwardstravel direction of the valve spool 6, the relationships are reversed tothe effect that the pressure supply port P then supplies the utilityport A via the corresponding associated control grooves 30 and theutility port B is then fluidically connected to the return port T2. Inthis case the middle cross channel 56, with the control diaphragm 62fully opened, is supplied via the pressure supply port P with fluid viathe control chamber 12 and the two further control diaphragms 60 and 64move to close their free cross sections, wherein until then the barrierdevice according to the invention continues to function via thedescribed channel routing in conjunction with the longitudinal channel50, thus heating the fluid by friction in the area of the diaphragms 60and 64. If the diaphragms 60 and 64 are completely closed and thediaphragm 62 is completely open, the reduced cross section of the crosschannel 56 at the pressure supply port P still results in a reduced flowrate with increased resistance, i.e., frictional heat is generated inthe fluid at this point.

In summary, it can therefore be concluded that the actual heatingfunction is implemented via said bypass diaphragms 60, 62, 64 in thevalve spool piston 6, to which end the preferably steady-state pressureat the pressure port P is connected to the two tank channels T1, T2 in atype of bypass. When the valve is actuated in the manner described so asto move it out of its illustrated closed middle position, the bypass, asexplained, is closed for both actuation directions of the valve spool 6.With normal actuation of the valve, in other words in pressurizing thecorresponding utility port A or B, there is consequently no longer anydirect slippage which, after having flowed through the barrier device,is supplied with the one type of control diaphragms 60, 62, 64. Apressure that is preferably settled by means of a (not shown) pressurecompensator at the pressure supply port P has the advantage that thesize in the closed middle position of the valve, in which the utilityports A, B are not pressurized, is defined such that the slippage forheating does not depend on the pump pressure at the pressure supply portP. Because of the small size of the aforesaid diaphragms 60, 62, 64 withregard to the maximum free cross sections thereof, during the heating ofthe fluid during operation there is hardly any dependency on theviscosity of said fluid and consequently on the temperature. Because theflow rate via the barrier device and through the connected channels Pand T1 and T2 is uniform, a uniform heating of the valve block, over theentire extension thereof, can be assumed. This is without parallel inthe prior art.

1. A valve comprising a valve housing (2), which has at least oneutility port (A, B), at least one pressure supply port (P) and at leastone return port (T1, T2) and a valve spool (6) guided in the valvehousing (2) in a longitudinally displaceable manner, for transporting aheatable fluid, such as hydraulic fluid, characterized in that in atleast one position of the valve spool (6), in which the pressure supplyport (P) is separated, at least in part, from the utility port (A, B),the heatable fluid reaches, starting from this pressure supply port (P),via a heat-emitting connection in the valve spool (6), the at least onereturn port (T1, T2) as slippage, which serving as a heat source heatsat least areas of the valve spool (6).
 2. The valve according to claim1, characterized in that the slippage can be heated via a barrier devicewhich, serving as a fluid resistance, transfers heat generated byfriction to the fluid entering and/or exiting the valve spool (6). 3.The valve according to claim 1, characterized in that the barrier devicehas at least one type of control diaphragm (60, 62, 64), of which thefree diaphragm cross section in the control mode results from a closingmotion of the valve spool (6) relative to the valve housing (2) in thearea of the one pressure supply port (A) and/or of the one return port(T1, T2), into which port or into which ports the heat-emittingconnection in the valve spool (6) opens.
 4. The valve according to claim1, characterized in that, with increasing widening of the diaphragmcross section of the one type of control diaphragm (62) at the onepressure supply connection (P) with simultaneous narrowing of the same(60, 64) at the one return connection (T1, T2), by means of another typeof control diaphragm (30), of which the free diaphragm cross section inthe control mode results from a closing motion of the valve spool (6)with respect to the valve housing (2) in the area of the one assignableutility connection (A, B), the flow rate from this one pressure supplyconnection (P) to this one assignable utility connection (A, B)increases.
 5. The valve according to claim 1, characterized in that theheat-emitting connection in the valve spool (6) is formed by alongitudinal channel (50), which in the control mode exits, by means ofcross channels (54, 56, 58), at least in part towards the one pressuresupply connection (P) and the one return port (T1, T2).
 6. The valveaccording to claim 1, characterized in that the one type of controldiaphragm (60, 62, 64) in the valve housing (2) has at least one recess(18, 20), which is permanently fluidically connected to the one pressuresupply port (P) or to the corresponding one return port (T1, T2), andthat the corresponding recess (18, 20) in the valve housing (2) iscovered by the valve spool (6).
 7. The valve according to claim 1,characterized in that the further type of control diaphragm is formed byat least two opposite groups of control grooves (30) at the outerperimeter of the control piston (6), which, starting from acircumferential annular recess (14, 16) in the control piston (6), tapertoward the ends.
 8. The valve according to claim 1, characterized inthat, in a neutral position of the control piston (6), two utility ports(A, B) are separated from the pressure supply port (P) and from the tworeturn ports (T1, T2), which are each operatively associated with arespective one of the utility ports (A, B).
 9. The valve according toclaim 1, characterized in that a control diaphragm of the one type or ofthe further type is associated with one return port (T1, T2) each andwith one utility port (A, B) each.
 10. The valve according to claim 1,characterized in that the control diaphragm (62) of the one type at thepressure supply port (P) closes and opens, respectively, upon theopening and closing of the control diaphragm (60, 64) of the one type atthe two return ports (T1, T2).